This invention relates to polycarbonates having substituted or unsubstituted carbamate terminal groups.
It is known that in the interfacial polymerization process to make aromatic polycarbonates from dihydric phenols and phosgene the use of small amounts of diverse chain terminators can be used to provide end or terminal groups. Examples of patents which disclose these known terminal groups are U.S. Pat. No. 3,085,992 Lee, et al. (alkanol amines) and U.S. Pat. No. 3,399,172, Jaquiss (imides).
It is also known from Schnell et al., U.S. Pat. No. 3,028,365 that aromatic amines and other mono-functional compounds can be used to control or regulate the molecular weight of the polycarbonates, thereby forming aryl carbamate terminal groups. However, aromatic amines, such as aniline, are known to be carcinogenic and thus should be avoided if at all possible. See for example "Chemical Carcinogens" by C. E. Searle pages 366-461 (1976) ACS Monograph 173.
According to Schnell on page 183 in his book "Chemistry and Physics of Polycarbonates" (1964), ammonium hydroxide and amines are known to saponify polycarbonates back to the monomers i.e. bisphenol A. This is confirmed by Bolgiano in U.S. Pat. No. 3,223,678 wherein he indicates that small amounts of amines such as monoethanolamine and morpholine break or degrade polycarbonates into lower molecular weight polycarbonates.